Back to the point (why would Russia need to feel threatened by NATO on its borders). Why was it agreed (verbally, as part of US and UK diplomacy with Russia) in 1991 that NATO should not expand an inch eastwards after the reunification of Germany?
The alleged discussions were in 1990, and were with the USSR, which subsequently ceased to exist. Only a select few of the attendees, all on the Soviet/Russian side, appear to have any recollection of those discussions reaching any agreeements, and even then the recollection was patchy at best. It was discussed, it appears, but it doesn't sound like any formal agreement was made, and it certainly didn't make it into the written agreements - why would the USSR have signed the agreements without that clause if it was both important and agreed. As it was, at that time, NATO was already at the the Ukrainian border with the USSR, so any agreement would have been relating to places like Finland and Sweden.
Regardless, any discussions would have been between NATO and a USSR which no longer exists, whereas this disagreement is between Ukraine and Russia. Long subsequent to those discussions Russia agreed to respect Ukraine's borders... look how that went.
There must have been an understanding that it would be inappropriate.
No, at the time there wouldn't even have been a sense in the USSR that Ukraine would ever exist as an independent nation, let alone that it might petition NATO for entry.
Then there was the Cuban missile crisis that resulted from the US having nukes in Italy.
That was certainly a significant element of it, yes. I'm failing to see how the cold war progression of land-based nuclear threats which have largely been replaced by ICBMs and submarine-launched systems is relevant to why Ukraine's sovereignty has been egregiously breached and whether it has the right to seek alliances to protect from a very apparent threat from an expansionist neighbour.
O.
